Electric furnace



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Patented June 24, 1924.

UNITED STATES PATENT OFFICE.

MORRIS H. BENNETT, OF WATERBURY, CON'NEQTICUT, ASSIGNOR T0 SCOVIL MANU- FACTURING COMPANY, A CORYORATION OF CONNECTICUT.

ELECTRIC FURNACE.

Application led June 26, 1918. Serial N0. 241,318.

To all 11i/wm t may concern:

Bc it. known that l, Mouais H. BENNE'rr, a citizen oil the lnited States, residing at lVuterburv, count)r of New Haven, and Stale of Connecticut, have invented certain new and useful Improvements in Electric Furnaces. fully described and represented in the following specification and the accompanying drawings. forming a part of the same.

.This invention, specifically considered; relates to improvements in electric controlling or regulating mechanism for electric furnaces. f

The amount of heat energy which can be economically. delivered to a furnace which employs electric energy as its source of heat, said ener y being-delivered to the charge through e ectrodes` is limited by various factors, such as-the size v'andimatcrial of the electrodes, the, capacity of the charge to economically absorb the heat and the capacity of the furnace ivallsto withstand radiatedheat. As' rapidity of operation is of the highest importance, the `heat energf) should be delivered to the furnace at the highest rate consistent with the limiting fac tors, and. where a plurality of electrodes are' employed.4 each electrode should always de liver as nearlyv as possible its predetermined proportion of such energy. A furnace working on a three-phase system, for instance. and employing three electrodesv` should be capacitated to so operate that a predetermined amount of heat energy will be delivered at a uniform rate by all the electrodes, that this predetermined heat input will he subdivided in a definite proportion among the electrodes` and that each electrode will uniformly deliver its proportion of the predetermined heat input.

:is however. metallurgical conditions are constantly changingr during the furnace op eration. the electrical conditions in the furnace :irc also constantly changing. lt is, therefore. obvious that the delivery of energy to the furnace must be controlled or regulated with respect to these changing conditions, or losses Will result which will seriously interfere with the economical op eration of the furnace.

Attempts have heretofore been commer cialhT made to meet the varying conditions in an electric furnace by automatically positioning the electrodes throughY devices ivhich depend for their. o eration-on .variarA tions in the amperagex e heat input does nou-however, depend solely on the amperage delivered, butfis 'afectedby other factors, such, for instance, as changes'iin W'att--4 age, orfchaiig'es in thepotential affectedby the* resistance between electrode" and charge, which will'serlouslyiinterfere witlLthe economical operation bfthe'furnacemndwhich would not be aidjusted for? by controlling devices which depend for their operationen changes in amperage Epri finstace, 'a' three-electrode" furnace provided f-vvitl1 a control dependingfsolely upon variations in' amperage, theiamperagefdelivered" by the' three'electrodes wouldbe the predetermined quantity desired,- but the proper distribution of the :heat'finput' betweenftheclectrodes might f not "be maintained. "For 1e'1mmple with such a furnace, one electrode may oyen be immersed'iand frozen inthe chargefa'nd -vet the an'iperage4 indicating devices 'ffwill show thelproper amper-age on'the systemi Of course, under vsuch conditions, uniform, distribution of. `the hea-t1 cannot be had.' Again. in starting=-the melting ofacharge, where amperage 'control -is-depe'nded on',the electrodes m'ust be initially setto'determine the resistance by a manual operation. Under these conditions. it may be tha-tan insufficient resistance -will beJ established between thc-electrodes and the charg'e,'and beca-use ofthis insuilicient resistance the resulting power factor-Will be'too` low for feconomical opera-tion, and yet the amperage indicating devices will `show the proper amperage on the system.

A primar7 object of this invention is to provide an improved electric controlling apparatus which, specifically considered, is specially applicable to 4.electric furnaces, although it may be used in 'other relations, by which a plurality of energy deliveringl devices on `a circuit areall caused to de iver and maintain the delivery of energy at a predetermined rate and each device to maintain the delivery of a predetermined proportion thereof.

A further object of the invention is to produce an improved electric controlling;r apparatus which, specifically considered, 1s specially applicable to electric furnaces, although it maybe used in other relations,

by which a plurality of energy delivering devices on a. working circuit shall, through proper automatic adjustment of resistance. all be caused to deliver and maintain the delivery .of energy at a predetermined inte,

A further object of the invention is to` produce a controlling mechanism for electric furnaces in which the potential of the energy delivered by the electrodes to the furnace is maintained substantially constant and such other electrical conditions as will ali'ect'the rate of effective heat input are so regulated and controlled as to cause said heat input.v to be at a predetermined rate. whereby rapidity of operation is attained withoutv local overheating.

The invention, has other objects in view not necessary to here specifically point out. but which will appear hereafter;

With the objects. specifically referred to and others in view, the invention consists in certain elements, improvements. and combinations as will be hereinafter described and then specifically pointed out.

The accompanying drawing represents diagranimatically a. preferred embodiment of the improvedcontrolling mechanism in connection witha.. furnace, the furnace sclected for illustration being of the threephase, three electrode type.

In the drawing, l represents a furnace which4 is of usual construction, the electrodes being indicated. at 2, 3 and 4. A usual type ottransforrner is indicated at T., the circuits from the: transformer to the electrodes beingr respectively marked 5, 6 and 7. The primary switch ofi the transformer is indicated 8, and the connection with the high tension powerlines n.9, 1,0 and. 11-

Qonstructions embodying the invention will employ controlling mechanism of such a character that variations in the potential of the energy delivered will be adjusted for so that this potential is maintained substantially; constant. In what are regarded as the best. constructions, the controlling mechanism will be of such a character as to cause the electrodes to deliver and maintain the delivery of'heat energy to the furnace at a predetermined rate and each electrode'to deliver and maintain the delivery of a predetermined proportion thereof. lVhile this may beiaccomplished in various ways, it will. usually be accomplished by means which will adjust the resistance to meet varying conditions in the furnace. In preferred constructions embodying the inrention, and where the invention is cinployed in connection with electric furnaces. the resistance adjusting means employed will lie preferably such as lo adjust the re sistnnce between the electrodes and charge. ll'hilc this may bc variously accomplished, in the particular construction illustraled. the resistance is adjusted by shifting the position of the electrodes with respect to the charge. The devices illustrated for thus shifting or positioning thc electrodes to adjust the resistance are well-known electrode shifting devices and include three electric motors, the drums of which are indicated at 12, lf3, 14. Cable connections 11j. 16 and 17 run from the motor drums to yokes 1S, 19 and 20. these yokes being connected with the electrodes in an obvious way.

lhere electric motor mechanisms. such as have been referred to. are employed for shifting the electrodes to adjust the resistance, the construction and connections should be such that the motors can be operstcd in either direction to raise or lower the electrodes. As shown, the drum shafts of the motors are provided with worm wheels 21, 22 and 23. The fields of the motors are indicated at 24, 25, at 26, 27, and at 28, 29, respectively, the commutators of the armatures being indicated at 80, 31 and 32. The worm 'shafts for driving the worm wheels are indicated at 30', 31 and 32' rcspectively.

In the construction illustrated, the current for the motors is obtained from a main line circuit 33 which has branches 34, 35' and 36, these branches leading to the commutator brushes, In the particular constructionillustrated, the returns from the motor fields of the motors are by way of circuits which are normally open. The return :from the field 24 is by way of a w'irev 37'leading to a contact 38 and the return from the Iield 25 is by way offa wire 39 leading to a contact 40. The circuit' is closed through eitherthe contact 38' or 40 by devices which will be hereinafter described, the return main line circuit bein marked 41. Similarly, the return from t e field 26 is through a wire 42, terminating in contact 43. The return from the field 27 is through a wire 44 leading to a contact 45. According as the circuit is closed by the devices, which will be hereinafter described, through contact 43 or 45, the circuit will be completed by the branch 46 to the main line circuit.

The fields 28, 29 are connected by wires 47 48 to the main line circuit through contacts 49, 50, the return to the main line circuit being marked 5].

The specific means for closin the motor circuits may be considerably varied. In the best constructions, and where motors and circuits such as have been described are employed, these means will include an actuator.

Many variations in actuator` construction are possible and within the scope of the invention, ln the particular construction shown. the actuator for the circuits including the f contacts 38. consists of a bar 52 pivoted lll at The end of this bar is formed as a Contact 54 which is in circuit with the branch 4].

Similar actuators .T15 and 56 are provided for controlling the circuits leading from the fields of the other motors.

The means employed for effecting the movement of the actuators to close the circuits may be Widely varied and will be varied in accordance with the type of actuator employed. Preferably. however. the operating means will be such that the actuator is differentially operated. Tn the best constructions embodying the .invention` two controlling units will be employed for operating the actuator. As has been indicated. one of these units will be sensitive to changes in the potential affected by the resistance. The character of the other unit will depend upon the specific electrical 'factor or factors which it is regarded as important to con trol to effect the desired regulation. ln furnace practice and where it is desired to obv tain high economy in heat utilization. this unit will be sensitive to changes inthe wattage of the circuit to be regulated.

In the particular construction illustrated, the unit which is sensitive to changes in the potential consists of three resistance-potential coils 57, 58, 59. The coil 58 is mounted on one end of the actuator har 52 and the coils 57 and 59. respectively, are located below and above the coil 58. As shown, these potential coils 57. 58. 59 are connected in series and the coil 59 is connected by a wire 60 'to a. bus bar 61. From this bus bar a wire 62 leads to the power circuit wire 7. The coil` 57 is connected by a wire 63 to a bus bar 65. This bus bar 65 is in circuit with the charge by a wire 66 and a suitable contact 67. The potential coils for the actuator 55, which controls the motor mechanism for the electrode 3, are connected to a bus bar 68 by a wire 69, this bus bar being in turn connected by a wire 70 to the circuit. wire 6 of the electrode 3. These coils are also connected by a wire 7l to the bus bar 65 which, as before pointed out, is in circuit with the charge through wire 66 and con tact 67.

power-ampere coils 74, 75. lVhere. as in the construction shown, the actuator is to be differentially operated. the power voltagecoil 73 will, as shown, be lnounted on the end of the actuator bar opposite to that which carries the potential coil 58.

In the construction shown, the coils 74, 75 are. connected in series. As these coils are amperage coils, and as the current flowing through them is intended to be proportional to the current on the power circuit, they should be connected up with this circuit. While this may be done in various ways, the coil 75 is connected by a Wire 76 to current transformer 77 which is connected in the power feed wire 7. The other leg of the current transformer 77 is connected by a.

wire 78 to the coil 74. It will be apparent,

therefore, that the current through the coils 74, 75 will vary in proportion to the current liowing through the power feed wire 7.

As has been stated, the coil 73 is a powervoltage coil, and, in the construction shown, the current flowing through it, isintended to vary in accordance with the voltage on the power circuit. The coil 73, therefore, should be connected to the power circuit. As shown, one side of this coil is connected by a wire 79 to the bus bar 61 which, as before described, is connected by a wire 62 to the power feed wire 7. In the best constructions, 4thecircuit for this coil '73 will contain a voltage adjusting means for predetermining the voltage impressed on the coil. This may be accomplished by connecting a rheostat in the circuit.. As shown, the co1l 73 is connected by a wire 8O to a rheostat, indicated at 81. From this rheostat the Vwire 82 connect-stoLt-he bus bar 68, which,

as beforestated, is connected by a wire 70 to the power feed wire 6.

The connections for the ampere-ge coils which assist in controlling electrode 3 are similar to thosewhichhave just been described. The ampere-ge coils for electrode 3 are connected in series and the upper and lower coils 83, 84 are connectedl by wires 85, 86 to a current transformer 87 connected in the power Afeed wire 6 for the electrode 3. The lower side of the voltage coil 88 is connected by a wire 89 to the bus bar 68 .and the upper side of the coil is connected by a wire 90 tothe bus bar, 72.' `An adjusting rheostat 91 is connected into this wire.

The same instrumentalities may be employed for controlling the electrode 4 that are illustrated and have been described in connection with electrodes 2 and 3. The potential coils are not shown,'but the amperage coils and the voltage coils are indicated at 92, 93, 94. The circuits for these coils are shown, but as the coils are symmetrically connected it is not regarded as necessary to specifically describe them.

In the operation of the mechanism, it betential coils (not shown) ing understood that the furnace is charged, that there is current ou the iuotor circuit, that the electrodes are lifted so as lo he clear of the charge. and that the actuator hars are in the position shown iu the drawinfr. that is` so that the motor circuits are open, the power line is energized through the switch 8. s soon as the power line 1s energized the potential coils for all the actuators are energized. Current flows from the power feed wire 7 of the electrode 2 through the wire the bus bar 6l. the wire 60, the coils 59, 58. 57. the wire G?, and the bus bar 65. `qirnilarly, the potential coils for the elerirofle 3 fire ennuh/,ed through the wire 70. the bus har fill, and the Wires 69 and 71. the wire Tt connecting to the bus bar G5. The connection for the powhicli form apart of the control for the electrode 4 are symmetrical, the circuit wireleading from the power feed Wire for this electrode being', however, shown at 95'. This wire 95 is connected to the bus bar 72 and the coils willzbe connected to this bus bar 72 and the busbar'. It will be observed that the groups of potential coils are Y connected.

Theenergizing of these potential coils causes-the Contact ends of the actuator bars to swing'down against the lower contacts 40, 45 and.49 for the motor circuits; This closes the" circuit through the` elds 25, 27 and; 29 of the motors?4 The'motors therefore, start andallowfy Vthe electrodes to-de scendcr-A -'At' thisV -timei'fit -ina'jvv be reinarlred,A voltage: is impressed Aon the 4voltage coils got the-other cont-rolling,units,-` but-there are no amperes :.Hbwing" through? the arnperei co'ilst'of thesefunits because ontsthecliighV resitance between: the endsI ofthe' electrodes and the charge. The'watt elementsofithe control are, therefore, at t-his time4 doingno work;T i.-e., exerting no= pull on the actuator bafrs. This condition continues, Ai. e-, the motor circuits remain closed through 'the fields-25,2729, until any oneg-any two, or all three of the electrodes make electrical connection with the charge: For the puri poses of description, it will b'e'assumed that electrode 2 makes connection with the-charge ahead of the electrodes 3 and 4. As soon as the electrode 2 ,touches the charge, a circuit is establishedthrough the connection 67 and wire 66 to the bus bar 65,-so that this bar has the same potential as the feed Wire7. The potential coils 59,4 58, 57 are, therefore, shouted and, consequently, deencrgized-- The actuator bar 52 will, therefore, swing away from the contact 40, thus breaking the motor circuit through the field 25 and stoppim@7r the motor. As pointed out, the stop-V ping of the motor occurs as soon as the elec-- trode is in contact with the charge, so that undue downward movement of the electrode which might have serious consequences is prevented. This feature is of importance in constructions in which the electrodes are positively driven down by the motors.

Proceeding on the assumption that the electrode 3 next makes contact with the charge. the same operations occur and tlu` motor for this electrode is stopped as soon as the electrode 3 comes in contact with the charge- 'hen. however, electrode 3 comes in contar-t with the charge, electrode 2 being already in Contact, current starts to lou'in the man: power circuit` with the result that the transformers 7T. 87 are energized. This energizes the ampere coils 74 and 75. voltage coil 73 of this unit was, of course, energized when the power feed Wires 7, 6 were energized. As the potential coils are now deeuergized. the" result is that the actuatcr hars for the electrodes 2V and 3 will ce swung ip-against the upper contacts 38 and 43, thus closingtheV inotor circuits through the fields 24 and 26 of the motors. The motors;- therefore/l start* to run :in a reverse direction` and;-pullr-theseelectrodes up. .as soon. 'however-,F as these electrodes nve away trom the cha e,' :-the=resistance bet-veen the charge an :"these electrodes increases vivitl'rthe result that: the potential coi lsdnegn to' beenrgizodithee. potential A. in-` creasing aslwthe' resistance increasesft the resistance-r 'incrmses' however,` .the amperes fidwingthrough the amperev coilszdecreases. The result isf -therefoieitllat-r the` torque ex'- e'rted -by-r tliepdtentiul'coils: increases 'as the resistanceizncnehsgz-and: the; torq'ueexerted by. Aithe 'watt unit-decreases asfth .resistance increases'.- :,rWlEhen thdf'welectrodesfhve, by their upward fmovement .Heem-'adjusted to obtain` the calculateda or?. predetermined resist ance whiclr shouldT exist bet-Ween? the ends of theffelectrodesand thei'char e, the' poten-- tial coi'ls 4will overcome the pu l o'fthe watt The unit Aon .thef actuator -bars 'With the resultthat the actuator-bars swing away'V from1 'the npper-contactstand thus break the circuits through the lields 24"and-`26.. These circuits will remain broken. as long-as the. predeterminedf resistance betweeneach electrode and' the-chargeismaintainech It will be obvious that as the resistance, between any electrode and the charge varies from 'the predetermined resistance 'either the ampere coils or the potential coils will be correspondingly energized or deenergized and the actuatorI electrode 4 has not made contact with the charge. lf this be the condition, it will happen that while the electrodes 2 and 3 are being moved up to ust the resistance, thc electrode 4 will be moving down. As soon, however, :is this electrode makes contact with the charge, the same controlling operations will take place through its coils and actuator bar until the resistance between this electrode and the charge is properly adjustedA While it has been assumed that the electrodes Q, and Al come down into contact with the charge in the order named, it is apparent that, through the mechanisms and by the constructions described, the resistance between mich electrode and the charge will be properly adjusted so that the predetermined resistnnce is obtained no matter in what order the electrodes descend. The melting of the metal will start, therefore, Yunder conditions where heat energy is being delivered to the charge by each electrode at a predetermined rate. It will further be apparent that if during the continued operation of the furnace anything occurs to change the resistance between any electrode and the charge and thus change the rate at which heat energy is beingr delivered by that electrode, the proper controlling unit for the electrode will be immediately brought into operation to readjust the resistance for that electrode. Further, if any change in the resistance between any electrode and the charge unbalances the proper distribution of voltage through the system, the proper controlling units for the electrodes aected will immediately effect the proper readjustment. All the electrodes will, therefore, maintain the delivery of the heat energy to the furnace at the predetermined rate, and each electrode will maintain the delivery of its proper proportion thereof. r

As has been indicated throughout the specification.V changes and variations' may be made in the constructions by which this invention is carried into effect. vention is not, therefore, to be limited to the particular construction illustrated and described.

What is claimed is l. In an electric furnace, the combination of a plurality of power circuits and a plurality of electrodes. and means for maintaining such eiiect-ive resistance in the circuits as will cause each electrode to deliver its proportion of energy and all the electrodes to deliver the energy at a predetermined rate.

2.. In an electric furnace, the combination of a plurality of power circuits and a plurality of electrodes`v and means for automatically maintaining such effective resistance in the circuits as will cause all the The inelectrodes to deliver the energy at a predetermined rate and each electrode to deliver its proportion thereof, the resistance beingr automatically maintained at the maximum for these conditions.

In an electric furnace, the combination of a plurality of circuits and a plurality of` electrodes, said electrodes being spaced from the charge and thereby providing a..

resistance across which the energy is delivered, and means for maintaining such spacing and resistance as will cause all theelectrodes to deliver energy at a predetermined rate and each electrode to deliver its proportion thereof.

4.-. In an electric furnace, the combination with aisource of electric energy, of a pluraiity of circuits and a plurality of electrodes, and an automatic controlling mechanism operated by any substantial variation in the power delivered for maintaining such resistance in each circuit as Willcause all the electrodes to deliver energy at a predetermined rate and each electrode to deliver its proportion thereof.

I n an electric furnace, the combinationwith a source of electric energy, of a plurality of circuits and a plurality of electrodes` and an automaticcontrolling mech. anism thrown into-.operation by any sub,-

stantial variation in the resist-ance between' electrode and charge, said mechanism causingall the electrodes to deliver energy` at a predetermined rate and each electrode to deliver its proportionthereof.

6. In an electric furnace, the combination with a source of electric energy, of a plurality :of circuits and a plurality of electrodes, and an automatic controlling mechanism thrown, into operation by any substantial variation either in the resistance or in the power delivered, said mechanism causing all the electrodes to deliver ener at a redeterminedrateand each electro e to de iver its proportion thereof.4

7. The combination, in an electric furnace, of suitable power circuits and electrodes, anda controlling mechanism operating to maintain substantially-constant the potential of the energy delivered by the electrodes, and to so regulate and control the other electrical conditions-affecting the rate of effective heat input as to enabie a rapid heat input at a redermined rate to be had,v whereby loca overheating is avoided and rapidity of melting is attained.

8. The combinatlon, in an electric furnace, of suitable power circuits and electrodes, and a controlling mechanism. for so adjusting the resistance as tomaintain substantially constant the potential of the energy delivered by the electrodes and to regulate the other electric conditions affecting the rate of effective heat input as to enable a rapid heat input at a predetercircuit having gi `plu-'Palijiy' Vofelectrodes.l

mined vrate to be had, whereby local over heating is avoided and rapidity of melting is attained.

9. The combination, in an electric iur- Anoce, of Suitable power circuits and electrodes, and a controlling mechanism for so adjustinv the resistance between electrede .and ciarge as to maintain substantially constant the potential of the energy delivered by the electrodes and to regulate the other electric conditions affecting thejrete of effective heat input as to enable a rapid heat input at a predetermined rate to be had, whereby local overheating is avoided and rapidity of melting is attained. "l0/The combination, in an electric furnace, of suitable power circuits and electrodes, said electrodes being so positioned with respect to the charge as to provide a resistance across which the energy is delivered, an. a controlling mechanism, said controlling `mechanism including means for adjusting he"resistauce to maint-ain substntill'y constant the'potent-ial of the ener- `delivered by the electrodes, and means vrl.' dusti-rigthe resistance to so regulate andi cntrol :ihe other electrical conditions ectin herate of effective-heat input as to'iirb-'a apdheatn ut at a predeterbe :hakwjereby local ovei` h etin v-isavoided and rapidity of melting is-ttemed. i

-i 111.'. -an a-parntus for delivering electric energy inc uding a power delivering controlling Inehe'nism' :comprising an eleme 't #rendered effective "bya c lange in potential of--t'he energy delivered -by the electrodes-andan element rendered eiectveby'ichangefin tliewattage .of the power delivering "circuit, jsaidcontrclling mechanismopeiuting to regulate the Aenergy delivered by the electrodes.

121111 an a params 'for delivering electrical energy'ytfe'combination with a source of saiden'e'i ',foa circuit including a plurality of devices for delivering the energy flowing in to said circuit, and a controlling mechanism for ceusing all of'said devices to''deliver energtv -at 'a' predetermined rate and each device to deliver-a defi-nite proportion thereoft said cont-rolling mechanism including snclement rendered ell'eetive'by chungein otential of the energy delivered by any device and an element rendered electii've by a ,change in wattage.

13. In an apparatus for delivering elet:- trieal energy` the combination with a source of said energy. of a cilcuit including a plurality ol devices for delivering the energy flowing through said circuitand a controlmechanism including au element rendered effective by change in potential in ilu: energy delivered by any device, au clement renderedA veli'ective `by a change in wattage7 and an actuator differentially controlled 'oy said elements, said controlling mechanism causing all the devices to deliver energy at a predetermined rate and each device ro deliver a definite proportion thereofV 14. In an apparatus for delivering electrical energy, the combination with a source of said energy, of a circ-uit including a pluruht)v of devices for delivering the energy flowing through the circuit,7 and :i control nuclmnism including au element. rendered eli'ective bya change in potential of the energy delivered by any devicr an element rendered el'ective by change in wattage, an actuator diiierentially controlled by said elements, and resistance adjusting devices controlled by the actuator.

l5` .in :1n electric furnace, the combination of a source of electric energy. a circuit including a. plurality ol electrodes for delivering the energy flowing through the circuit to the furnace. and a control mechanism including an element rendered etlective by a change in potential of the energ)` delivered by any electrode and an element rendered ell'ective by a change in wattage, said control mechanism also including an actuator differentially controlled by the elements and operating throughsuitable meallS to. adjust the resistance between the electrodes and the furnace charge, whereby the electrodes are caused to deliver energy at a predetermined rate and-each electrode to deliver Aa definite proportion thereof.

16. In an apparatus for delivering electrical energy, the combination of a. source o said .'energy, -acircuit through which said enerq'"floivs,.-a n`d a controlmechanism for regulatin the flow of energy, said mechanism inciding an element rendered eil'ective by Vchanges in potential, and a second element-rendered edective by changes in wattage.

17. In an' apparatus for delivering electrical energy, the combination of a' source of said energy, a circuit through which vsaid energy flows, and a control mechanism for regulating the flow of encrgv through said circ-uit, said mechanism including an element operating by change in potential :in clement operated by change iu wattage, an actuator dilerentially controlled by said elements, and resistance controlling mecha` nism controlled by the actuator.

18. In an electrical rtguatiuv apparatus, the combination with a resis ice, of an electrically operated control i1 .ding an clement sensitive to ci in the potential :i tier-ted by the resistance, an element sensitivi: to changes in wattage` and sets of circuit connections for cach of said elements` whereby either :i change. in the potential or a change in wattage causes au adjustment of the resistance 19. ln the combination as claimed in 18,

an actuator through which the adjustment of the resistance is effected, said actuator being differentially controlled by said elements.

20. In an electric furnace, the combination with an electrode, of an electrically operated controlling mechanism for adjusting the resistance between electrode and charge, said mechanism including an element sensitive to changes in the potential affected by the resistance, an element sensitive to changes in wattage, and sets of circuit connections for said elements, whereby either a change in the potential or a change in wattage causes an adjustment ofthe resistance between the electrodes and charge.

2l. In the combination as claimed in 19, an actuator through which the adjustment of the resistance is etfected, said actuator being differentially controlled by said elements.

22. In an electric furnace, the combination` with the electrodes', of electrically operated controller mechanism, said controller mechanism including mechanism for shifting the relative position of the electrodes and charge and thereby adjusting the resistance, said mechanism also including an element sensitive to change in the potential affected by the resistance and an element sensitive to changes in wattage, and sets of circuit connections for each of said elements, whereby either a change in the potential or a change in Wattage causes an adjustment of the resistance.

23. In the combination as claimed in 22, an actuator for operating the shifting mechanism,l said actuator being differentially controlled by said elements.

24. In an electric furnace, the combina` tion with a plurality of electrodes, of a shifting mechanism, independent connections from the shifting mechanism to the electrodes, whereby the electrodes may be independently shifted to adjust the resistance between eachelectrode and charge, a set of controllingelements for each electrode, said elements including an elementNsensitive to changes in the potential affected b the resistance between the electrode an charge, and an element sensitive to changes in wattage, sets of circuit connections for said elements, and means whereby said elements effect the operation of the shifting mechanism.

25. The combination as claimed in 24, an actuator for each electrode differentially operated by the controlling'elements for that electrode, and means whereby the actuator effects the 4operation of the shifting mechanism.

26. In an electric regulating apparatus thc combination with operating circuits, of an actuator for controlling said circuits and operating units for the actuator, one of said operating units being rendered effective by changes in potential and the other of said units being rendered effective by changes in wattage, the arrangement of the actuator being such that it is differentially controlled by the units,

27. In an electric furnace, the combination with a plurality of electrodes, of a motor mechanism for shifting the electrodes toadjust the resistance between the electrodes and the charge, independent connections from the motor mechanism to the electrodes, whereby the electrodes may be independently shifted, suitable circuit. connections for the motor mechanism whereby the motors ma)Y run in either direction, actuators for controlling said motor circuits, controlling units for the actuators sensitive to changes in the potential affected by the resistance between the electrodes and the charge, and controlling units for the actuators affected by changes in wattage, said units being arranged to differentially control the movement of the actuators.

28. In an electric regulating apparatus, the combination with a plurality of operating circuits, of a plurality of pivoted actuator bars one for each circuit for control-` ling the circuits, a controlling unit sensitive to changes in potential for moving the bar in one direction, and a controlling unit sensitive to changes in wattage for moving the bar in the o posite direction. A

29. In an electric furnace, the combination with a plurality of electrodes, of a sourcfof electric energy with which the electrodes are in circuit, a motor mechanism, connections between said motor mechanism and each electrode, whereby the electrodes maybe independently shifted to adjust the resistance between the electrodes and the charge, normally open motor mechanism operating circuits one for each electrode, contacts in said circuts whereby the circuits may be closed in either direction throu h the motor mechanism, and a control mec anism for said operating circuits, said control mechanism including a plurality of actuator bars, a controlling unit .for each actuator bar affected by changes in potential affected by the resistance between the electrodes and the charge and a controlling unit for each actuator bar affected by changes in wattage in the power circuit, said controlling units being arranged to differentially operate the actuator bars to close the circuits through the contacts, whereby changes in potential or wattage causes the actuator bars tosc control the motor circuits as because the motors' to run in the proper direction.

30. In an electric furnace, the combination with a power circuit, of a plurality of electrodes, means whereby the electrodes are caused to descend into contact with the charge when the power circuit is closed, and

:i controlling mechanism including means for automatically stopping the downward movement o any electrode when that electrode comes in Contact with the charge.

31. In an electric furnace, the combination with a power circuit, of a plurality of eleotrodes, means for moving 4the electrodes to bring them into contact with the charge and for thereafter :shifting them to establish lo a predetermined resistance between each electrode and the charge, and a controlling mechanism operating Lo properly position the electrodes and establish a prcfleleriiiineri resistnrce between each elect-rode and the charge irrespective of the order in which the electrodes come in Contact. with the charge.

In testimony whereof, I have hereunto ser my hand.

MORRIS H. BENNET"`, 

